1. Field of the Invention
The present invention relates to a method and device for producing highly compressed cylindrical bales from loose stalk material, such as hay or straw, and more particularly, to a method and device for producing bales of varying length.
2. Discussion of the Related Art
Briquetting presses of various forms are well known. A briquette is a volume of stalk material which, when highly compressed, forms a bale. These bales usually have a diameter of 10 to 15 cm and a length corresponding approximately to this diameter. The density of such stalk material briquettes is typically between 350 and 500 kg/m.sup.3 and in extreme cases as high as 800 kg/m.sup.3.
One such briquetting press is disclosed in U.S. Pat. No. 3,244,088. The rolling space of this press is formed, for example, by six press rollers which can be pivoted with respect to the axis of the rolling space. In addition, the rolling space has a slightly conical design in order to facilitate the emergence of a rotating compressed roll conveyed continuously axially out of the rolling space. The compressed roll emerging from the rolling space is cut by a cutting device, which directly follows the rolling space into individual briquettes whose length may be shorter than their diameter.
A comparable briquetting press can be found in DE-A-1 176 418. In this press, the rolling space is formed by four or five positively driven press rollers which define a conical rolling space. As a result of the conical widening of the rolling space, the rolled up material is continuously pushed out of the winding space under rotation and pressed into a cylinder, where it is braked by adjustable springs. The cylinder and springs rotate in the same direction and with the same speed as the flow of material. Briquettes are then cut to the desired size from the roll of material with the aid of break-off teeth which grip through longitudinal slots of a cylinder jacket. During the cutting operation, the springs serve to hold back the rolled ball remaining in the rolling chamber against the action of the break-off teeth.
DE-A1-3 609 631 discloses an alternative briquetting press, in which cutting blades are successively radially pressed into the compressed roll emerging from the rolling space. These blades protrude radially from a cutting wheel, which is driven by the blades and the feed of the compressed roll, and thereby cut off the bales. With this driving of the cutting wheel, the blades are pressed relatively slowly into the compressed roll, which for this purpose is carried by two pairs of conveying rollers. The conveying rollers thus receive the brunt of the considerable pressure applied by the blades. It is difficult for this pressure to be absorbed by the conveying rollers, since intermediate spaces must necessarily remain between the conveying rollers, so that the stalk material of the compressed roll can be squeezed through. Consequently, this increases the risk that the compressed roll or the briquette will disintegrate.
A common disadvantage to all these briquetting methods and balers is that, as a result of the rotation of the compressed roll and the centrifugal forces consequently acting on the stalk material, and as a result of the cutting forces exerted by the cutting element on the compressed roll, the rolled briquettes become less dense at their surface so that there is a tendency to disintegrate to a large extent during cutting or during the subsequent handling, and are thus of no use to the farmer. To resolve this disadvantage, worldwide developmental work on continuous pick-up briquetting presses or rolling devices having axially emerging compressed rolls, and subsequent cutting devices for these compressed rolls, has been carried out for decades both by science and industry, but has never progressed beyond the trial stage and has finally been abandoned in practice.
So-called large rolling bale presses are to be distinguished from the briquetting presses described above. The former, very widespread presses in practice, produce rolled bales which usually have a diameter of 100 to 150 cm and a dry matter density of only about 100 to 120 kg/m.sup.3. Thus, for example, DE-A2-2 443 838 discloses a discontinuous rolling tale press, in which the ready bales situated in the rolling space are bound with a binding means, such as a twine or a web of net or film. By swivelling the rear part of the rolling space housing, the bound bale is removed therefrom. Then, the rolling space is again closed. During the binding and the opening and closing of the rolling space, the machine must be brought to a standstill.
EP-A3-0 268 002 discloses a continuous rolling bale press, wherein the pressing space of conical design is formed by a plurality of press rollers. The pressing space, which is open at the end face of greater diameter and which is to be loaded in the circumferential direction, produces a compressed roll flowing out at the open end face with axial and continuous feed. Thus, the diameter of the compressed roll corresponds to that of conventional rolled bales. Immediately following the pressing space is a cylindrical conveying section, having a wall which is formed by driven conveying rollers arranged with their axes of rotation mutually parallel and together form a conveying channel. The diameter of the conveying channel is approximately the same as that of the compressed roll emerging continuously axially from the pressing space. (Behind the pressing space and in the region of the conveying section, a binding device is provided for binding the compressed roll, which is still subject to radial pressure, during its axial feed. The binding is carried out using a binding means delivered between two of said conveying rollers. Following the binding device is a cutting device, which can be arranged either in the region of the conveying section or immediately following.